1. Field of the Invention
The present invention relates to a collision detecting device for motor vehicles which is adapted to actuate a restraint system such as an air bag system upon detection of a collision of the vehicle.
2. Description of the Prior Art
In Japanese Utility Model Publication No. 60-35939, there has been proposed a collision detecting device of this kind which comprises a rotary member having the center of gravity positioned eccentrically from its rotational axis and a cam portion provided thereon and an electrical contact mechanism arranged to generate a collision signal therefrom when it has been brought into contact with the cam portion of the rotary member in the occurrence of a collision of the vehicle. The collision detecting device can be constructed by a relatively small number of component parts without causing any difficulty in assembly, and the electrical contact mechanism can be arranged to provide high reliability in operation. The electrical contact mechanism is, however, designed to be brought into contact with the cam portion of the rotary member only at one point. It is, therefore, required to preclude failure caused by secular change of the contact point.
To satisfy the requirement for the contact point, it has been considered to use gold-plated contacts in the electrical contact mechanism. It has been, however, found that each gold layer on the contacts becomes a porous layer through which copper components of the base plate for the contacts is precipitated due to chemical change and deposited on the surfaces of the contacts to cause insufficient conduction of the electrical contact mechanism. It has been also found that contaminants, water and defaced particles in the ambient atmosphere are adhered to the surfaces of the contacts to cause insufficient conduction of the electrical contact mechanism. In the collision detecting device to be actuated only in an accident, it is very important to eliminate such insufficient conduction of the electrical contact mechanism in a reliable manner.